Wegovy vs Mounjaro: Complete Comparison

Overview: What Are Wegovy and Mounjaro?

Both Wegovy and Mounjaro are injectable medications that revolutionized weight loss treatment. They belong to a class of drugs called glucagon-like peptide-1 (GLP-1) receptor agonists, and one is a dual GLP-1/GIP agonist.

Wegovy is the brand name for semaglutide when used for chronic weight management. Semaglutide is also sold as Ozempic for type 2 diabetes. Wegovy was approved by the FDA in June 2021 for weight loss in adults with obesity or overweight with weight-related health conditions.

Mounjaro is the brand name for tirzepatide for type 2 diabetes management. Tirzepatide is also sold as Zepbound, which is the weight loss-specific formulation approved in November 2023. Many doctors prescribe Mounjaro off-label for weight loss because it\'s often more affordable despite being technically approved for diabetes only.

Mechanism of Action: Single vs. Dual Agonist

The fundamental difference between these medications lies in their mechanisms of action. Understanding this difference explains why Mounjaro produces slightly greater weight loss.

Wegovy (Semaglutide): Single GLP-1 Agonist

Wegovy activates only GLP-1 receptors, which are found throughout the brain and gastrointestinal system. This single mechanism is highly effective for weight loss and has been extensively studied.

• Reduces appetite through central nervous system signaling
• Slows gastric emptying, promoting satiety
• Improves insulin secretion and glucose metabolism
• Increases energy expenditure moderately

Mounjaro (Tirzepatide): Dual GLP-1/GIP Agonist

Mounjaro activates receptors for both GLP-1 and GIP (glucose-dependent insulinotropic polypeptide). This dual mechanism provides additive effects that explain its superior weight loss outcomes.

• GLP-1 activation reduces appetite and slows gastric emptying
• GIP activation significantly enhances energy expenditure
• Combined effect produces greater weight loss than single-agonist approach
• Improves metabolic markers and insulin sensitivity more effectively

Clinical Trial Results: STEP vs SURMOUNT

The most compelling evidence comes from large clinical trials. Wegovy\'s efficacy was demonstrated through the STEP trials, while Mounjaro\'s (tirzepatide) was demonstrated through the SURMOUNT trials.

STEP Trials (Wegovy/Semaglutide)

• STEP-4: 17.4% average weight loss at 2.4 mg dose (n=803)
• STEP-3: 17.6% average weight loss (n=611)
• STEP-2: 10.1% average weight loss at lower doses
• STEP-1: 15.3% weight loss in initial Phase 3 trial
• Duration: 68 weeks of treatment
• Comparator: Placebo controls

SURMOUNT Trials (Mounjaro/Tirzepatide)

• SURMOUNT-3: 21.4% average weight loss at 15 mg dose (n=731)
• SURMOUNT-2: 21% average weight loss (n=639)
• SURMOUNT-1: 22.5% average weight loss at highest dose
• Duration: 68 weeks of treatment
• Comparison: Superior to semaglutide in head-to-head studies
• Most participants had type 2 diabetes or prediabetes

Weight Loss Efficacy: Head-to-Head Comparison

Based on clinical trial data, Mounjaro (tirzepatide) produces greater average weight loss than Wegovy (semaglutide). The difference is approximately 4-5% body weight, which translates to 10-20 additional pounds for many patients.

Important caveat: Average weight loss doesn\'t predict individual outcomes. Genetics, baseline weight, adherence to lifestyle changes, and metabolism significantly influence results with either medication. Some patients respond better to Wegovy, while others achieve superior results with Mounjaro.

Dosing Schedules and Titration

Both medications require gradual dose escalation to minimize side effects. However, their dosing schedules and available dose ranges differ significantly.

Wegovy (Semaglutide) Dosing

• Starting dose: 0.25 mg injected subcutaneously once weekly
• Titration: Increases by 0.25 mg weekly for 4 weeks, then 0.5 mg increments
• Available doses: 0.25 mg, 0.5 mg, 1 mg, 1.7 mg, 2.4 mg
• Max recommended dose: 2.4 mg weekly
• Typical duration to max dose: 8-16 weeks
• Injection type: Multi-dose pen or pre-filled pens

Mounjaro (Tirzepatide) Dosing

• Starting dose: 2.5 mg injected subcutaneously once weekly
• Titration: Increases by 2.5 mg every 4 weeks
• Available doses: 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg
• Max recommended dose: 15 mg weekly
• Typical duration to max dose: 12-16 weeks
• Injection type: Pre-filled single-dose pens

Key difference: Mounjaro uses higher absolute doses (mg) but maintains the same efficacy, suggesting greater potency. Wegovy requires a longer overall titration period due to smaller dose increments, which may delay reaching therapeutic doses but allows more gradual adaptation.

Side Effects and Tolerability

Both medications have similar side effect profiles dominated by gastrointestinal symptoms. Mounjaro may cause slightly more GI effects due to its more potent mechanism, but differences are minimal.

Common Side Effects (Both Medications)

• Nausea: 25-40% of patients (most common, usually transient)
• Vomiting: 5-12% of patients
• Diarrhea: 20-23% of patients
• Constipation: 15-20% of patients
• Abdominal pain: 15% of patients
• Appetite reduction: Desired effect, but can be excessive

Serious Adverse Events (Rare)

• Pancreatitis: Rare but serious; discontinue immediately if suspected
• Gallbladder issues: May increase with rapid weight loss
• Severe allergic reactions: Very rare
• Hypoglycemia: If combined with diabetes medications
• Retinopathy: Possible in diabetic patients (requires monitoring)

Side effects are typically dose-dependent and improve after 2-4 weeks on each new dose. Eating smaller meals, staying hydrated, and taking medication with food can help manage gastrointestinal symptoms.

Cost and Insurance Coverage

Cost is a critical factor in medication selection. While both have similar retail prices, insurance coverage differs significantly based on the indication (weight loss vs. diabetes).

Retail Pricing (Without Insurance)

• Wegovy: Approximately $1,320-$1,400 per month (4 pens)
• Mounjaro: Approximately $1,350-$1,450 per month (4 pens)
• Difference: Negligible; both are expensive

Insurance Coverage

• Wegovy: Approved for weight loss; increasing insurance coverage
• Mounjaro: Approved for diabetes; often better covered for diabetes indication
• Off-label use: Mounjaro commonly prescribed off-label for weight loss (may have better coverage)
• Prior authorization often required for both
• Medicare does NOT cover weight loss medications
• Medicaid coverage varies significantly by state

Copay Assistance Programs

• Novo Nordisk (Wegovy): Copay cards reducing costs to $0-$250/month for eligible patients
• Eli Lilly (Mounjaro/Zepbound): Similar copay reduction programs available
• GoodRx: May offer discounts at certain pharmacies
• Manufacturer programs: Direct discount programs may be available

Cost strategy: Despite Mounjaro\'s higher retail price, it may be more affordable if prescribed for diabetes instead of weight loss, as diabetes medications often have better insurance coverage. Always check with your insurance and ask about copay assistance before making your decision.

Quick Comparison Table

Who Should Choose Wegovy vs Mounjaro?

Choose Wegovy If:

• You prefer a medication with more established long-term safety data (approved 2021)
• You want a single-mechanism medication with potentially fewer side effects
• You prefer smaller dose increments for more gradual adaptation
• Your insurance strongly prefers Wegovy for weight loss indication

Choose Mounjaro If:

• You want maximum weight loss potential (4-5% greater average weight loss)
• You have prediabetes or type 2 diabetes (dual metabolic benefits)
• Your insurance covers Mounjaro better as a diabetes medication
• You prefer a more potent medication despite potentially more side effects initially

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